Technical Field
Embodiments of the subject matter disclosed herein generally relate to marine seismic systems. More specifically, the embodiments relate to systems and methods for passively and automatically controlling the payout length of cables connecting seismic sources and/or receivers to floats.
Discussion of the Background
Marine seismic surveys involve a vessel towing one or more sources and one or more receivers across a survey area, which involves a number of cables connecting various parts of the marine seismic survey system. As illustrated in FIG. 1, a marine seismic survey system 100 includes a vessel 102 that tows a plurality of streamers 110 (only one is visible in the figure) and a seismic source 130. Streamer 110 is attached through a lead-in cable (or other cables) 112 to vessel 102, while source 130 is attached through an umbilical 132 to the vessel. A head float 114 floats at the water surface 104 and is connected through a cable 116 to a head end 110A of streamer 110, while a tail float 118 is connected through a similar cable 116 to a tail end 110B of streamer 110.
Source elements 136 are connected to float 137 by respective cables 135 so that the source elements 136 travel at desired depths below the water surface 104. During operation, vessel 102 follows a predetermined path T while source elements 136 emit seismic waves 140. These waves bounce off the ocean bottom 142 and other layer interfaces below the ocean bottom 142 and propagate as reflected/refracted waves 144 that are recorded by seismic receivers 122.
Deployment and recovery of the components of marine seismic survey systems can be complicated by any one of the various cables becoming twisted or tangled around other cables or components. This can damage components of the system, which can be quite costly. Even when components are not damaged, the delay incurred to untangle the cables and/or equipment can also be quite expensive because of the amount of fuel expended by the vessel as well as payment of the crew during this downtime.
Accordingly, it would be desirable to provide devices, systems and methods to reduce the possibility that cables can become twisted or tangled during deployment and recovery of seismic survey equipment.